Regex Tester

Write a regular expression and see every match highlighted live, with capture groups and a replace preview.

FreeNo sign-upRuns in your browserMobile-friendly

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What does the Regex Tester do?

Type a pattern and flags, paste test text, and matches are highlighted instantly. The table lists each match with its position, numbered groups ($1, $2…) and named groups. Add a replacement string to preview String.replace results.

The tester uses your browser’s JavaScript regex engine, so results match what your JavaScript code will do. It stops after 500 ms to protect you from patterns with catastrophic backtracking.

How to use the Regex Tester

  1. Enter the regex without slashes, and flags such as g, i or m.
  2. Paste your test text.
  3. Inspect highlighted matches and the groups table.
  4. Optionally enter a replacement to preview.

Examples

Emails

Pattern (\w+)@(\w+)\.com on “ali@example.com” captures “ali” and “example”.

Reformat dates

Pattern (\d{2})/(\d{2})/(\d{4}) with replacement $3-$2-$1.

Common use cases

  • Building validation patterns
  • Writing search-and-replace rules
  • Learning regular expressions
  • Debugging log parsing

Features and benefits

  • Private by design — your data is processed on your device and never uploaded.
  • Free with no account, no watermark and no usage limits.
  • Works on phones, tablets and desktops in any modern browser.

Limitations to know

  • JavaScript regex differs from PCRE, Python and .NET in some features.

Frequently asked questions

Which flags are supported?

g, i, m, s, u, y and d.

Why does my pattern freeze other sites?

Nested quantifiers like (a+)+ can backtrack exponentially. This tester stops after 500 ms.

Do I include the slashes?

No, enter only the pattern.

Embed this tool on your website

Add the free Regex Tester to your blog or website. Paste the code into your page’s HTML; the tool runs in your visitors’ browsers and stays up to date automatically. Please keep the credit line below the tool.

Free to use on any website. The tool runs inside an iframe served from viptools.pk; nothing your visitors type is sent to your site or ours. Preview the embedded version.

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